Fuel cells are electrochemical cells in which a free energy change resulting from a fuel oxidation reaction is converted into electrical energy. As shown in FIG. 1, a typical fuel cell 10 consists of a fuel electrode (anode) 12 and an oxidant electrode (cathode) 14, separated by an ion-conducting electrolyte 16. The electrodes are connected electrically to a load (such as an electronic circuit) 18 by an external circuit conductor 20. In the circuit conductor, electric current is transported by the flow of electrons, whereas in the electrolyte it is transported by the flow of ions, such as the hydrogen ion (H.sup.+) in acid electrolytes, or the hydroxyl ion (OH.sup.-) in alkaline electrolytes. In theory, any substance capable of chemical oxidation that can be supplied continuously (as a gas or fluid) can be oxidized galvanically as the fuel 13 at the anode 12 of a fuel cell. Similarly, the oxidant 15 can be any material that can be reduced at a sufficient rate. Gaseous hydrogen has become the fuel of choice for most applications and the most common oxidant is gaseous oxygen, which is readily and economically available from the air for fuel cells used in terrestrial applications. When gaseous hydrogen and oxygen are used as fuel and oxidant, the electrodes are porous to permit the gas-electrolyte junction to be as efficient as possible. The electrodes must be electronic conductors, and possess the appropriate reactivity to give significant reaction rates. The most common fuel cells are of the hydrogen-oxygen variety that employ an acid electrolyte. At the anode 12, incoming hydrogen gas 13 ionizes to produce hydrogen ions and electrons. Since the electrolyte is a non-electronic conductor, the electrons flow away from the anode via the metallic external circuit. At the cathode 14, oxygen gas 15 reacts with the hydrogen ions migrating through the electrolyte 16 and the incoming electrons from the external circuit to produce water as a byproduct. Depending on the operating temperature of the cell, the byproduct water may enter the electrolyte, thereby diluting it and increasing its volume, or be extracted through the cathode as vapor. The overall reaction that takes place in the fuel cell is the sum of the anode and cathode reactions; in the present case, the combination of hydrogen with oxygen to produce water, with part of the free energy of reaction released directly as electrical energy. The difference between this available free energy and the heat of reaction is produced as heat. It can be seen that as long as hydrogen and oxygen are fed to the fuel cell, the flow of electric current will be sustained by electronic flow in the external circuit and ionic flow in the electrolyte.
In practice, a number of fuel cells are normally stacked or `ganged` together to form a fuel cell assembly. The anode/electrolyte/cathode sub-unit is typically referred to as an `electrode assembly` (EA). The cathode of the first EA is typically disposed next to the anode of a subsequent EA, but separated by a bipolar plate. The bipolar plate is typically carbon, chosen for its unique combination of properties; chemical inertness, electrical conductivity, rigidity and the ability to be machined. A network of channels are typically formed in the bipolar plate by mechanical machining to distribute the fuel and oxidant to the anode and cathode respectively. The bipolar plate provides electrical connection from one EA to the next, and also serves to isolate the anode fuel from the cathode oxidant in adjacent EA's. In order to further contain the fuel and keep it separate from the oxidant, a sealing means, such as an o-ring or other exterior gasket, is needed. Other traditional types of fuel cells use extremely complex stacking arrangements consisting of a membrane, gaskets, channels, electrodes and current collectors that are difficult and expensive to fabricate and assemble, and are highly subject to catastrophic failure of the entire system if a leak develops. As can be easily appreciated, the cost of fabricating and assembling fuel cells is significant, due to the materials and labor involved. Typically, 85% of a fuel cell's cost is attributable to manufacturing costs. Thus, the complexity of prior art fuel cell structures is one of the factors preventing widespread acceptance of fuel cell technology. An improved style of fuel cell that is less complex and less prone to failure would be a significant addition to the field.